3. Selection of embryos without embryos
Due to the legal situation in some countries the number of embryos that are allowed to be generated during a treatment cycle is limited to the number of three. Therefore, on the day after oocyte retrieval, when the oocytes have reached the pronuclear state, those three PNā€™s have to be selected for further embryo culture and the other PNā€™s might be kryopreserved. Up to recently no reliable criteria were available to choose the three good ones out of a set of zygotes. In view of the fact that only 30-40% of all fertilised oocytes attain the ability to implant this selection was nothing else but a lottery. In some other countries with a less strict legislation all available and good oocytes are allowed to develop to embryos and can be watched during embryo culture. Then, one or two embryos that show a normal development are selected and transferred into the uterus, which results in a high pregnancy rate without the risk of a triplet pregnancy.
Now criteria are being elaborated that are increasingly reliable in determining the further growth potential of oocytes shortly after fertilization. A selection of the "good embryosā€¯ before they are embryos. A giant step for patients living in countries with a strict legislation.
Wittemer C, Bettahar-Lebugle K, Ohl J, Rongieres C, Nisand I, Gerlinger P (2000) Zygote evaluation: an efficient tool for embryo selection. Hum. Reprod. 15: 2591-2597
4. Y chromosome analysis of infertile men and their sons conceived through intracytoplasmatic sperm injection
The Y chromosome is inherited from the father to the son. Thus, microdeletions on the Y chromosome that are associated with severely impaired spermatogenesis and require intracytoplasmatic sperm injection for parenthood may be transmitted to the son via ICSI. In order to study the prevalence of microdeletions in consecutive 86 men that required ICSI and fathered a son the Y chromosomes of the fathers and their sons were analysed for microdeletions. Fifty of the 86 men (56%) had idiopathic seminiferous tubule failure (STF); the remainder had a variety of other indications for ICSI. Deletions were found in two (6.9%) of 29 azoo- or severely oligospermic men with STF. Identical deletions were found in their respective sons. No de novo deletions were detected in the remaining 97 sons conceived by men without deletions. The study demonstrates that deletions on the Y chromosome are encountered only in very severe cases of STF and if deletions are observed in sons following ICSI they are transmitted vertically via ICSI. De novo deletions appear to be very rare.
Cram DS et al (2000) Y chromosome analysis of infertile men and their sons conceived through intracytoplasmatic sperm injection: vertical transmission of deletions and rarity of de novo deletions. Fertil Steril 74: 909-915